Solvent extraction process



SOLVENT EXTRACTION PROCESS Filed Sept. 14, 1939 ATFINATE ou 71.57'

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55% n @www resented July 29, 194iy :amie

' SOINENT EXTBCTION IIBOCESB arm o. Gillespie, creams, N. r. um i. standard oil Development Company. a corporation of Delaware .innemen september u, im, seria N. 29cm The present invention relates to cerned with the treatment of petroleum oils with a particular class of selective solvents. In accordancewith the present invention, petroleum -oils, particularly petroleum oils boiling in the range below about 420 F., are segregatedk into their relatively morearomatic fractions and into their relativelyzmore parafiinic fractions by means of solvents selected from the class of nitro alcohols which are characterized by having 'a hydroxyl group and a nitro group on adjacent carbon atoms and are further characterized by having anaromatic or oleilnic group attached to one of said carbon atoms.

' It is well known in the'art'to treat mineral oils, particularly petroleum oils, with various selective solvents which have the ability to segregate the relatively more aromatic fractions from the relatively more paramnic fractions. In processes of this character, the oil and solvent `are suitably contacted by various processes, as for example,by a single batch process or by a multi batch process. In general, the preferred process,

however, is a countercurrent tower treating operation in which the lighter phase, usuallythe oil,

- is introduced into the center or bottom section optimum values to secure desirable results and depend upon various factors, as for example, upon the particular solvent or solvent mixture being used, the oil being treated, and theyield and quality of the products desired. These processes are usually employed in the solvent treatment of petroleum oils in order to improvevtheir quality and in order to segregate particularly desirable fractions. In treating these oils, solvents of the class ,which have a preferential selectivity for the more aromatic type compounds as compared to the more paramnic type compounds are usually employed. Solvents of this class are, for example, phenol, furfural, sulfur dioxide, cresol, nitro benzene, aniline, beta beta dichlor diethyl ether, and the like. Mixtures of those petroleum oils boiling below` about 420 F.

The conditions of operation are adjusted to 5 Claims. (Cl. IDG-13) the solvent treatment oi' minerai oils and is especially con-V the ability to modify the selectivity'and solvent power ofthe selective solvent of the type of water, glycols, and alcohols are also employed.

AThese latter materials may b'eadded to the respective phases after separation or may be introduced intothe countercurrent treating system at a plurality of points.

I have now discovered a class of solvents which are particularly desirable in the treatment of petroleum oils,` especially for the treatment of The'solvents of my invention vare selected from the class of nitro alcohols which may be represented by the following structural formula:

Y. xv z---w E IIIOI in which at least one of W, X, Y, and Z represents an aromatic or oleflnic radical. Solvents of thisv class are, for example, alphahydroxy-beta-nitroisobutylbenzene, produced by reacting. benzaldehyde with Z-nitro propane; 4-hydroxy-5-nitrohexene-2, produced by reacting crotonaldehyde -with nitroethane; phenyl nitromethyl carbinol;

nitro benzhydryl carbinol: l-styryl-l-hydroxy-2- v nitro 2 methylpropane: 3 hydroxy-4-nitro-4- phenylpentene-l: alphahydroxy-beta-nitro-'betaposes of illustration it is assumed that a heavy' naphtha boiling in the range from about l250' F. to 400 F. is being solvent treated with alphahydroxy beta nitro-isobutylbenzene, Tower I represents a countercurrent solvent treating tower containing suitable distributing and contacting means. The heavy naphtha is introduced into tower I by means of feed line 2. The heavy naphtha flows upwardly through tower I and contacts downflowing solvent which is introduced into tower I by means of feed line l. Temperature and pressure conditions are maintained on tower I in order to secure the formation of a ramnate phase and a solvent extract'- phase. The ramnate phase is withdrawn from-tower' I by means of line I and treated in a. manner to sepa'- rate the solvent from the oil. If desired, a partial phase separation may be secured in Y ramnate separator l and the precipitated solvent these solvents are also utilized, as well as substances of the class of liquened normally gaseous returned to tower I by means of 11net. The

'rai'.llnate is removed from` solvent separator i by means of line 1 and introduced into ramnate stili 8 in which the final traces of raffinate are removed from the solvent. The solvent is removed from still 8 by means of line 9, while the solventfree raftinate is removed by means of line I0, In case the treated stock is heavier than the solvent, the solvent, of course, would be taken overhead through the line I 0, and the solvent free raiiinate would be removed as bottoms through line 9. The

solvent extract is withdrawn from tower I by means of line II and also handled in a manner to separate the oil from the solvent. If desired, a partial phase separation may be securedin solvent extract separator I2 and the precipitated oil returned to tower I by means of line I3. The solvent extract is withdrawn from solventl separator I2 and introduced into solvent extract still I4 by means of line I5. The solvent-free extract is removed overhead from solvent extract still I4 by means of line I6, while the solvent is removed bymeans of line I 'I. The selectivity and solvent power of the solvent may be modified by the introduction of solvent modifying agents by means of lines I8. I9, and 20. Phase separation in the raffinate separator .'il and in the solvent extract separator I2 may be facilitated by the introduction of a precipitant by means of lines 2I and 22 respectively, by cooling, or by other equivalent means.

The process of the present invention may vary widely. Although any solvent having the structural formula as given in which at least one of It is preferred to use atmospheric pressure or a' pressure sufficient to prevent undue vaporization of the feed oil being treated and to employ a temperature below the complete mlscibility temperature of the oil and the solvent. The temperature necessarily must be above the crystallization temperature of the normally solid solvent. For example, when using alphahydroxy-betanitro-isobutylbenzene, the temperature is preferably in the range from about 60 F. to 120 F. depending upon the feed oil being treated. Although the solvents of the present invention may be utilized in the relatively pure state, their' selectivity and solvent power may be modified by the addition of solvent modifying agents.

Inorder to illustrate the invention, the following example is given which should not be construed as limiting the same in any manner whatsoever:

EXAMPLE A heavy naphtha boiling in the range from about 225 F. to 410 F. and containing about 30% by volume of aromatics was treated withK various selective solvents of the present invention. The results of these opera'tions which were carried out in single batch extraction operation were as follows:

` TABLE Naphtha extractions with nitroalcohol solvents ofthe type WXCNOZCOHYZ Alphahydroxy- Phenylnitro- Nitrobenz- Name of solvent methyl ls'iti? hydryl carbinol bewege carbinol Group represented by letter ol general formula:

Hydrogen.-. Methyl Ph'enyl. -...do do Do.

Hydrogen.... Hydrogen. Z henyl Do. Solvent treat on naphtha containing vol. percent of aromatica, vol. percent on feed 100 100. Temperature of extraction, "F 100... 100. Extract yield, vol. percent on feed 18.5; 14.0. Rafinate yield, vol. percent on ieed 81.5. 86.0. Concentration of aromatics in extract,

vol. percent on extract 85.5 80.4 85.3.

W, X, Y, and Z represents an aromatic or olenic radical may be used, preferred results are secured when at least one phenyl group is attached to a carbon atom to which the hydroxyl or nitro group is attached. Preferred solvents are thus `nitro alcohols characterized by having the hydroxyl group and the nitro group attached to adjacent carbon atoms and which are further characterized by having at least one aromatic group. particularly at least one Iphenyl group, attached to the carbon atom to which the hydroxyl or nitro group is attached. Thus the preferred solvents are for example, solvents of the types of alpha-hydroxy-beta-nitro-isobutylbenzene, phenyl nitromethyl carbinol, nitro-benzhydryl carbinol, alpha hydroxy-beta-nitro-beta-phenyl-npropylbenzene, and 2-nitro-2-phenyl-3-hydroxybutane.

The volume of solvent used per volume of oil being treated will depend upon the particular solvent being used, as well as upon the feed oil being solvent treated and also upon the yield and quality of products desired. In general it is preferred to use from one-half to four volumes of solvent per volume of oil being treated. The temperature and pressure conditions are likewise adjusted to secure optimum results and depend,

in general, upon the above enumerated factors.

From the above data it is apparent that relatively high yields of substantially pure aromatic fractions may be secured when'utilizing the solvents of the present invention. It will be noted that the high concentration of aromatics attained in the extracts indicates unusually good selectivity for the solvents.` Since the extract yield is relatively high for a single batch treat, only a small number of countercurrent stages will be adequate to remove substantially all of the aromatics from the feed. The extracts thus obtained will possess a higher concentration of aromatics than was attained by batch operation, and the yields will be correspondingly increased.

Extracts approaching 99-100% aromatics concentration for use as high octane blending agents, high solvency naphthas, chemical raw materials, and the like may be easily obtained by the use of the solvents herein disclosed in conjunction with a light paralnic hydrocarbon such as propane or butane. These may be prepared by reextracting the primary extracts obtained as above together with about 100% (on extract) of the light parafhnic hydrocarbon with one of the solvents of my invention. 'I'he secondary extract phase thus obtained, after removal of the light parafllnic hydrocarbon and the solvent, consists of practically pure aromatics.

oils into their relatively more aromatic and into their relatively more paramnicconstituents comprising contacting said petroleum oils with a 10.

solvent,- selected from the class of solvents which formula are characterized by the following structural' wherein at leastone of the' members W., X, Y, and Z is an aromatic group. and the remaining members are selected from the class consisting 2 of hydrogen and hydrocarbon.- groups. under conl ditions to form a solvent extract phase and a rainate phase. separating the respective phases and recovering the solvent therefrom.

2. Process for the segregation of petroleum 25 oils boiling in the range below about 420 F. into their relatively more aromatic andinto their relatively more parafiinic fractions comprising contactingsaid petroleum oils with a solvent. selected from the class of nitro alcohols which l are characterized by having the following structural formula:

Y x z--JIi-'w 0 NOI wherein at least one of the members W, X,'Y.'

and Z is a phenyl group, and the remaining members are selected from the class consisting of hydrogen and hydrocarbon groups,under conditions to form a solvent extract phase. and a raffinate phase. separating the respective phases and recovering the solvent therefrom.

3. Process in accordance with claim 2 in which said solvent is phenylnitromethyl carbinol.

4. Process in accordance with claim 2 in which said solvent is alphahydroxy-beta-nitro-isobutyl-- benzene. v

5. Process in accordance with claim 2 in which said solventv is nitro-benzhydryl carbinol.

Banca c. GrrLasPm. 

